1 Field of the Invention
The present invention relates generally to systems and methods for network switching, and more particularly to efficient routing of communication paths in a telecommunications system.
2. Related Art
A conventional Common Channel Signaling (CCS) telecommunications network comprises three basic components: Customer Premises Equipments (CPEs; for example, a private branch exchange (PBX)), communications busses (also known as links; for example, telephone lines) and nodes (for example, switches). The switches are used to selectively connect the CPEs via the links. A CCS network is characterized by the separation of signaling links and traffic links. Switches in a CCS network establish traffic links between CPEs by exchanging signaling messages via signaling links that specify tasks to be performed on the traffic links. The format of these signaling messages is typically specified by a standard.
One such standard is the Integrated Services Digital Network (ISDN) User Part (ISUP) standard, referred to hereinafter as "the standard" or "the ISUP standard." The North American ISUP standard is presented in a document entitled "American National Standards Institute (ANSI) Signaling System No. 7 (SS7) Integrated Services Digital Network (ISDN) User Part (ISUP), ANSI T1.113 (1995)," which is incorporated herein by reference in its entirety. The international ISUP standard is also presented in a document entitled "ITU-T Recommendation Q.763 Signaling System No. 7 (SS7) Integrated Services Digital Network (ISDN) User Part (ISUP), Formats and Codes."
The standard specifies a set of signaling messages that a network must support in order to comply with the standard. Each of these signaling messages must be accompanied by one or more parameters; these parameters are also defined by the standard. The standard also provides for several "spare" parameters. Spare parameters are of two types. Under the ANSI ISUP standard, these two types are referred to as "reserved" and "network specific." Under the ITU ISUP standard, a country can develop a country-specific ISUP standard; under such a standard, the "network specific" parameters are generally referred to "country specific."
Reserved spare parameters are those that are not currently defined by the standard, but that may be defined by the standard at some future time. Network service providers are free to use the network specific spare parameters to transmit proprietary data to implement proprietary services to supplement those provided by the standard. A service provider will typically offer many proprietary services, and thus will require many spare parameters to implement those services. When a service provider exhausts the network specific spare parameters, he has little recourse but to employ some of the reserved spare parameters.
However, if a service provider employs a reserved spare parameter to implement a proprietary feature, and subsequently redefines that spare parameter, the service provider will no longer be in compliance with the standard. In order to comply with the new standard, the service provider must redefine the proprietary feature to use a different spare parameter. To implement such a parameter change, a service provider must change the call processing software in its network switches. This is an expensive and time-consuming task. Further, if the newly-selected spare parameter is a reserved spare parameter, it may subsequently be re-assigned. Thus, this solution is not a permanent one. Further, a service provider may require more spare parameters than are available.
What is needed, therefore, is a method for transmitting proprietary data that is independent of the reserved spare parameter data structure specified by the standard.